Heat exchanger



April 1, 1947.

w. PARRISH HEAT EXCHANGE! '7 Sheets-Sheet 1 Filed Dec. 10. 1943 A '11947- w. c. PARRISH HEAT BXCHANGER 7 Filed D60. 10, 1943 7 Sheets-Sheet2 April 1, 1947- w. C. PARRlSI-l ,1

HEAT EXCHANGE! Filed Dec. 10, 1943 7 Sheets-Sheet s April .1, 1947. w cPARRISH' 2,418,191

HEAT EXCHANGER Filed Dec. 10, 1943 7 Sheets-Sheet4 ZIPPER I 180 April 1,1947.

W. C. PARRISH HEAT EXCHANGER Filed Dec. 10, 1943 7 Sheets-Sheet 5 April1, 1947. w. c. PARRISH ,1

HEAT EXCHANGER 7 Filed Dec. 10, 1943 7 Sheets-Sheet 6 April I, 1947.

w. c. PARRESH HEAT EXCHANGER Filed Dec. 10, 1945 7 Sheets-Sheet '7exhaust gases.

gether with the end tabs 52, are welded together in edge to edgerelation, and thus form the divider 26 previously referred to. The edgesof the deflector strips 50 are weldedto the tube 30, to the cylindricalsheets 34 to 46, and to the case ing 24, so as to provide airtightindividual passageways extending through the heat exchanger. Forexample, the hot fluid entering the manifold 20 will be deflectedthrough an angle of 90 by the helical portions 54 of the deflectorstrips at the inlet end, will flow substantially longitudinally betweenthe longitudinal portions 56 of the deflector'strips, and will, at theoutlet end, he deflected an additional90 in the same direction as theinitial deflection, so that the hot fluid entering the manifold 20 will,in the course of its flow through the heat exchanger, be transposed 180?and will, therefore, be discharged through I thehot fluid manifold 2|.In a similar manner, the cold air entering manifold 22 will be deflectedthrough a total of 180 in the course of its flow through the heatexchanger, and will be discharged through the manifold 23.- In thisarrangement, the helical portions at opposite ends of each of the strips50 extend in opposite directions from the straight intermediate portioncircumferentially of the heater.

By comparison of Figs. 5 and 6, it will be observed that in the spacebetween the tube 30 and the innermost cylindrical sheet 34, thedeflection of the fluid entering the top portion of the heat exchangerwill be in a clockwise, direction, whereas in the space between sheets34 and 35, the deflection of the hot fluid entering-the manifold will be180 in the counterclockwise direction. Similarly, the deflection of thefluid in the spaces between the successive cylindrical sheets 34 to 4Band the casing 24 will be alternately in op- I heat exchanger. 1

exchanger maybe made of aluminum or other light weight metals, or theiralloys.

As shown by the arrows in thevarious figures, the two fluids flow inopposite directions through the heat exchanger but this is not essentialif the difference in initial temperatures of the two heat exchanger maybe used as a secondary unit, that is, as a means to transfer heat 'toatmospheric or cabin air from air which has been heated by exhaust gasesin a primary heat exchanger. In this latter system it will usually befound to be desirable, if notnecessary, to utilize the counter-flowprinciple in the secondary In my improved arrangement, comprising theclosed tube 30, the concentric cylinders 34' to 4B and the outer casing24, the space between each two adjacent cylindrical walls is divided bydeflector strips into two sections, with one section preferably carryingheating fluid and the other section preferably carrying fluid to beheated. At'the extreme end, the deflector strips are positionedhorizontally at opposite sides of the device so as to provide an uppersection and a lower section, such strips being deflectedcircumferentially so as to bring the strips into vertical position atthe intermediate portion of the device and thus provide a section ateach side of the device, the strips being further deflectedcircumferentially so as to bring the opposite end portions again intohorizontal position at opposite sides and providing upper and lowersections.

In this arrangement, the circumferential deflection of the strips 50 forthe innermost sections next to the closed tube 30 is in clockwisedirection, while the circumferential deflection of the strips for thenext adjacent sections is in a counposite directions, thus providing hotand cold fluids on the opposite sides of each of the cylindrical sheets34 to 46. This feature of the con- 'struction may be most readilycomprehended by comparing Figs. '7, 8, and 9. Due to this arrangement,the construction of the heat exchanger is greatly strengthened since thehelical portions of alternate deflector strips, proceeding radiallyoutward from the center of the heat exchanger, lie in different planesand thus serve beter as reinforcements of the cylindrical sheets.Because of this arrangement, the cylindrical sheets may be made verythin and the overall weight of the heat exchanger is thereby reduced.

In most installations it is desirable torhave all of the passagewaysthrough the heat exchanger of substantially equal cross-sectional areas,so that the pressure drop due to friction will be substantially uniformacross all passageways. In this way the temperature gradient along theheater will be uniform in the different passageways and there will notbe any tendency for the walls of some of the passageways tobecomeexcessively heated. It will be noted that in Figs. 3 and 4 the sheets 34to 46 and casing 24 are spaced progressively closer together toaccomplish this result.

All of the parts of the heat exchanger are preferably made of stainlesssteel sheets whenever one of the fluids is of a corrosive nature, or ofextremely high temperature, such as the engine Due to the arrangement ofthe concentric sheets and the deflector strips, the

sheet metal may be very thin, sheets in the orderof .007" in thicknessbeing found satisfactory. When both fluids are not extremely hot and areof a non-corrosive nature, the parts of the heat terclockwise direction,the direction of deflection of the strips changing for each two sectionsas compared with the two sections next adjacent thereto. This causes thestrips in each cylinder 1 to be in crossed relationship with respect tothe single inlet manifold connected with all of the strips in the nextadjacent cylinders, so as to bunched inlet portions of the passagewaysat the top at one end of the device to direct fluid into alternatesections at both sides of the device, and by the use of a single inletmanifold connected with all of the bunched inlet portions of thepassageways at the top at the opposite end of the device to direct fluidinto all of the remaining sections of the device. In like manner twooutlet manifolds, one at each end and each connected with all of theoutlet portions of the passageways at that end, are adapted to receivethe fluid passing through the device, the outlet portions ,of thepassageways at each end being bunched at the bottom half of the devicefor convenient connection of the'manifold thereto.

In some installations, especially those wherein the volumetric rate offlow of onefluid is considerably in excess of said rate of flow of theother fluid, it becomes desirable to provide an inequality ofcross-sectional area in the flow paths of the two fluids, a larger flowarea being. assigned the fluid having the higher volumetric rate so asto prevent such fluid from undergoing an excessive drop in pressureduring flow through the exchangers A construction embodying thisprinciple of having the hot and 00111 fluid passageways oi unequalcross-sectional area is dis- .7

closed in Figs. 10, 11 and 12.- The portion of the heat exchanger shownin these flgiires is adapted to be assembled with manifolds of the typeshown in Figs. 1 and 2, and is to be used in essentially the samemanner. Although the flow of the two fluids through the exchanger isshown in Figs. 10,

11 and 12, as being in the same general direction, this is not essentialand the unit may be used with fluids flowing in opposite directionsshould zontal center line' is in alignment with the longithe conditionof the installation require and war- 4 rant such flow condition.

The heat exchanger comprises a central closed end tube 80 and eccentriccylindrical sheets 82, 84, and 86 with intermediate sheets 83 and 85 andthe external casing 81 concentric with the central tube 80. Deflectorstrips 90 are oi gen-' erally the same form as the deflector strips 50,

but are of tapering width conforming to the in which the are located. ll s ivith deflector strips 50, the deflector strips 90, if desired, canbe so constructed as to deflect the fluid at the} exit end, 90 in adirection gen.- erally opposite to the initial deflection, instead of 90in a direction generally the same as the initial deflection. In thearrangement shown in the drawings, however, the deflection of the fluidentering either the upper passageway or the lower passageway between thewall of the casing 81 and the cylindrical sheet 86 extends through 180degrees in counterclockwise direction in Fig. 12, and this is true ofthe deflection of the fluid entering either the upper passageway or thelower passageway between the cylindrical sheets 85 and 84, and true ofthe deflection of the fluid entering either the upper passageway or thelower passageway between the cylindrical sheets 83 and 82.

The deflection of the fluid entering the remaining three upperpassageways or the remaining three lower passageways, as shown in Fig.12, extends in each instance through 180 degrees in clockwise direction.

The cylindrical sheets 82 to 8'? are so spaced relative to one anotherthat the areas of the inlet ends of the various passageways are equal.However, it will be noted that the major portion of the inlet area ofeach of the passageways above the horizontal center line is in alignmentwith the longitudinal portion of the passageway. For example, the inletpassageway at the top between the cylindrical sheets 83 and 84 increasesin size toward the right in Fig.12 so that the major portion of theinlet is located in the upper right hand quarter of said flgure, suchmajor portion being thus in alignment with the longitudinally extendingportion of the passageway. The inlet passageway at the top between thecylindrical sheets at and 85, on the contrary, increases in size towardthe left in said figure so that the major portion of said inlet islocated in the upper left hand quarter of said figure, such majorportion being in this instance also in alignment with the longitudinallyextending portion of the passageway. Similarly, it will be clear from aconsideration of Figs. 11 and 12 that the inlet above the dividerbetween the central tube 80 and the innermost cylindrical sheet 82 hasthe greater portion of its area to the right as viewed in Figs. 11 and12. The deflector 90 on the inner portion of the tube 80 has the helicaland blocking the space between the tube 80 and sheet 82 to the left asviewed in the figures, and serving as'a baille or tudinal portion of thepassageway. This reversal of conditions in connection with thepassageways below the horizontal central line in Fig. 12 is due to thefact that the upper inlet passageways increase in the same directioncircumferentially as that in which the deflection of the fluid iseffected,

while the lower passageways increase in the opposite directioncircumferentially from that in which the deflection of the fluid takesplace. The

' pp r passageways may be used for the hot fluid,

while the lower passageways fluid.

When the heat exchanger of Figs. 10 to 12 is employed in an airplane andutilizes the engine exhaust gases as a source of heat, the gravimetricflow rate of the exhaust gases will ordinarily are used for the cold bemuch greater, and the density much less,

than that of the air to be heated. The resultant high volumetric flowrate of exhaust gas is accommodated by the heat exchanger at arelatively low velocity offlow, resulting in a low pressure drop, byreason of the fact that the cross-sectional area of the hot fluidpassageways is so much greater than would be the case were thecylindrical sheets all placed concentrically about the central tube asin the construction shown in Figs. 1 to 9. On the other hand, while thepressure drop across'the cold air passageways is increased as comparedwith the pressure drop in the constructions of- Figs. 1 to 9, this isnot of great importance, because of the much lower volumetric flow rateof the cool air which is to .be

heated.

Generally speaking, the loss of heat due to the Entrance, or exit, of afluid into, or. out of, a

heat exchanger is proportional to the square of the velocity of flow,the proportionality factor increasing with increasing value, in excessof 1. of the ratio oi. the flow area immediately preceding or followingentrance to, or exit from, the heat exchanger to the flow areaimmediately after entrance to, or prior to exit from, said heatexchanger. Since the ends of the passageways through the heat exchangerfor, each fluid occupy substantially the whole area of the end of theinlet manifold, the entrance losses will be negligible. Only the edgesof the circular sheets will be effective to reduce the totalcross-sectional area of the inlets to the passageways, and since thesesheets are very thin. their effect will be negligible.

In each ofthe embodiments of the invention,

the deflector strips 50, 90, as well as the cylindrical sheets, providesurfacesfor the transfer of heat, since each of these strips and sheetsprovides primary heat transfer surfaces; having the hot fluid on oneside and cold fluid on the other. Also, in both embodiments thedeflector strips are so arranged as to reinforce the cylindrical sheetsand to render the heat exchanger assembly structurally rigid. This is ofimportance since in some installations of the heat exchanger it mayproject partly through the skin oi the airplane so as, in effect, toconstitute a continuation of the skin.

In the latter type of installations, the fluids guide leading to thepassage formed to theright. are preferably arranged to flow in the samedirection, since one of the manifolds, such, for example, as themanifold 20, may be in the form of an air scoop or ram to provide forflow of ventilatin air through the heat exchanger, this ventilating airafter passing through the heat exchanger being discharged into the cabinthrough manifold 2|, to which a suitable'duct may be connected; On theother hand, the exhaust stack may be connected to the manifold 23' and,after passing through the heat exchanger, the exhaust gases may bedischarged through the manifold 22. The manifold 22 may be suitablyconstructed for the purpose, and be located in the air stream externalof the cabin skin, so that the velocity head of the exhaust gasesleaving this manifold may be effectively utilized to impart some addedspeed to the airplane due to the reactive jet propulsion effect of thegases discharged from the manifold.

Each embodiment of the invention may be modified by having the helicalportions of each deflector strip extend in opposite directions. In suchmodified forms of the invention the advantage of having the fluidstransposed 180 in their courseof flow through the heat exchangers wouldbe lost, but in some installations, other benefits may more thancompensate for this loss.

While I have shown and described particular embodiments of my invention,it will be apparent that numerous variations and modifications thereofmay be made without departing from the underlyin principles of theinvention. I, therefore, desire, by the following claims, in includewithin the scope of my invention all such variations and modificationsby which substantially the results of my invention may be obtainedthrough the use of substantially the same or equivalent means.

I claim:

1. A heat exchanger comprising, a plurality of cylindrical sheets ofdifierent diameters positioned one within the other, a plurality ofdeflector strips secured between uccessive sheets respectively, anddividing each space between adjacent cylindrical sheets into twoseparate passageways, said deflector strips having their inlet endsinalignment and secured to one another to form a diametral dividing stripand having their outlet ends transposed through an angle of 180 andsecured together to form a second diametral dividin strip parallel tothe first, and a plurality of mainfolds having ends semi-circular incross section and secured to said dividing strips and the outermost ofsaid cylindrical sheets.

2. The combination set. forth in claim 1, in which said cylindricalsheets are concentric and spaced to provide passageways equalcross-sectional area.

of substantially 8 3. The. combination set forth in claim in whichalternate cylindrical sheets are concentrio with one another andeccentrically located with respect to the remaining sheets.

.4. The combination set forth in claim 1, in which alternate cylindricalsheets are concentric with one another and eccentrically located withrespect to the remaining cylindrical sheets, the eccentricity beingalong the diameter at which the ends of said deflector strips arelocated.

5. The combination set forth in claim 1, in

which alternate cylindrical sheets are concentric with one another andeccentrically located with respect to the remaining sheets, and in whichthe areas of the inlet ends of the passageways are substantially equal.

6. A heat exchanger comprising a'plurality of cylinders of differentdiameters positioned one within the other in spaced relation, 9. pair ofdeflector strips positioned between each two ads jacent cylinders andfixed in position so as to divide the space into two passageways, eachofsaid deflector strips having a circumferential deflection throughsubstantially with the strips deflected in opposite directionscircumferentially in alternately positioned cylinders and with theinlets of the several passageways in horizontal alignment with eachother, a manifold connected with all of the passageways at the topportion of the device at one end communicatin through the passagewayswith a second manifold connected with all f the passageways at thebottom portion at the opposite end, and a manifold con- REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Noyes Jan. 9, 1940 Munday Aug.16, 1927 Mortensen Apr. 19, 1932 Boehm July 19, 1932 Rosenblad May. 25,1937 FOREIGN PATENTS Country Date British Mar. 11, 1884 British Mar. 23,1901 British Sept. 19, 1903 Number Shipman June 10, 1930'

